The present invention relates to torque converters employed in vehicles with automatic transmissions.
Conventionally, torque converters employed in automotive vehicles have been designed as close to a circular-shaped torus cross section as possible. The reason for this is that the circular shape provided a smooth turning of the fluid and thereby an efficient hydrodynamic torque transfer between the impeller and turbine in the torque converter. With vehicles employing front wheel drive, however, the vehicle packaging space limitations make packaging a torque converter with a circular-shaped torus cross section difficult. In particular, there is a need to reduce the axial length of the torque converter as much as possible. However, this must be accomplished while still maintaining a certain amount of efficiency in transferring torque.
As a result, some have produced torque converters with a somewhat axially-squashed torus cross section, also sometimes called an oval torus. There has been some success at a reduction in axial length with components having a radial pull type of blades. A radial pull type of casting or molding process is one where two die halves are separated with a radial motion in order to release a finished part from the dies. For a torque converter stator formed with this process, the shroud portion of the stator cannot be molded integrally with the stator hub and blades. It must be formed separately and then attached. This adds expense to the manufacturing process. Further, the dies employed in the radial pull process are relatively complicated and expensive. A less expensive and simpler process than the radial pull process is axial pull casting or molding. In this process, the two die halves are separated with an axial motion in order to release the finished part. As for stators with the axial pull type blades, attempting to reduce the axial length of the torque converter makes it difficult to package a stator with reasonable blade length. When attempting to obtain a great deal of reduction in the axial length of the torque converter with axial pull type blades, the efficiency of the torque converter becomes too low. Consequently, the axial length reduction of torque converters is generally less than thirty present as compared to a round torus shape.
Thus, it is desirable to have a torque converter with a substantially reduced axial length compared to a conventional round torus shaped cross section that allows for the use of axial pull blades, while maintaining adequate efficiency in transferring the torque through the torque converter.
In its embodiments, the present invention contemplates a torque converter for use in a vehicle with an engine, which has a crankshaft, and a transmission, which has an input shaft and a stator shaft. The torque converter includes a cover, adapted to rotatably mount to the crankshaft, an impeller having an impeller housing rotatably coupled to the cover, and a turbine, adapted to rotatably mount to the input shaft and located generally within the cover and impeller housing. The torque converter also includes a stator assembly, located generally between the impeller and the turbine, having a one-way clutch adapted to mount to the stator shaft, and having a stator hub, a stator shroud, and a plurality of axial pull blades that extend in a generally radial direction from the stator hub to the stator shroud, with axially straight intersections between the blades and the hub and between the blades and the stator shroud, and with the stator hub, stator shroud and stator blades integrally formed as a single unit and mounted on the one-way clutch.
An embodiment of the present invention allows for a torque converter with an axial reduction over a conventional round torus shaped cross section of greater than thirty percent while still maintaining adequate efficiency of the torque converter.
An advantage of the present invention is that a stator of a squashed torque converter can still be formed with the less expensive axial pull type blades, and yet still maintain a high level of efficiency in transferring torque.